The present invention relates to a system for driving the radiator cooling fan of a transverse, water-cooled vehicle engine, and more particularly, to such a system utilizing an endless power transmission belt.
In order to obtain the most efficient cooling of a water cooled vehicle engine, the radiator of the vehicle is normally disposed in a plane perpendicular to the vehicle axis (i.e., the direction of vehicle movement). A cooling fan is usually disposed in a plane parallel to the radiator, for the purpose of drawing air through the radiator to cool the liquid coolant circulating through the radiator. In the past, most vehicles made and sold in the United States had the engine mounted in-line (i.e., with the crankshaft parallel to the vehicle axis). In such vehicles, the radiator cooling fan was typically driven by a shaft extending from the vehicle water pump, the cooling fan either being mounted directly on the shaft, or being mounted on the output member of a viscous fluid coupling. In either case, the mounting of the cooling fan was fixed relative to the vehicle engine.
More recently, it has become common to mount the engine transversely of the vehicle, i.e., with the engine axis perpendicular to the vehicle axis. In such vehicles, the axis of the crankshaft and the axis of rotation of the cooling fan are not parallel, but instead, are disposed at right angles relative to each other. Thus, driving the radiator cooling fan by means of the engine crankshaft, either directly or indirectly, becomes more difficult, complicated, and expensive.
One of the prior art arrangements employs a pair of rigid shafts, interconnected by a set of bevel gears (see U.S. Pat. No. 3,613,654). Such an arrangement is relatively expensive, and in view of the number of other components and accessories in the engine compartment, it is extremely difficult to route a gear and shaft type drive system on most vehicle applications. In addition, having the cooling fan fixed relative to the engine requires that additional space be provided between the radiator and the fan, to accommodate movement of the engine relative to the radiator.
Another approach to driving a cooling fan from the crankshaft in a transverse engine vehicle is shown in U.S. Pat. No. 4,040,272, assigned to the assignee of the present invention. A flexible shaft is used to transmit rotational torque from the crankshaft to the fan. This arrangement requires that the flexible shaft undergo several changes of direction, or turns. In certain vehicle applications, especially in relatively smaller vehicles, the necessary routine of the flexible shaft results in several turns of relatively small radius. Operation under such conditions results in a substantially reduced torque capacity for the cable, or a substantially reduced endurance of the cable, or both.
Accordingly, it is an object of the present invention to provide an improved system for driving a radiator cooling fan of a transverse water-cooled engine.
It is another object of the present invention to provide a system which achieves the above-stated object, and which is relatively inexpensive, durable, and which comprises elements generally understood and accepted by the automative industry.
It is another object of the present invention to provide such a system which permits mounting of the cooling fan in a manner which results in optimum fan efficiency, and increased torque transmitting capacity.
The above and other objects of the present invention are accomplished by the provision of an improved system for driving a radiator cooling fan of a vehicle of the type including a vehicle frame and an engine which defines an axis of rotation and is mounted transversely of the vehicle axis. The system comprises a main drive pulley driven by the engine and rotating in a plane generally parallel to the vehicle axis. A fan drive assembly has the cooling fan operably associated therewith, the fan drive assembly defining an axis of rotation, and being fixedly mounted relative to the vehicle frame. The fan drive assembly includes a driven pulley rotating in a plane generally transverse to the vehicle axis. An endless power transmission belt is in driving engagement with the driven pulley, and in driven engagement with said main drive pulley. The belt includes a drive portion and a slack portion. Idler pulley means is provided having its axis fixedly mounted relative to either the vehicle frame or the engine, the idler pulley means being disposed forwardly of the main drive pulley, and transversely from the fan drive assembly. The idler pulley means engages the drive portion of the belt whereby said drive portion defines approximately a right angle. Also included is a belt tensioning device having a base portion fixedly mounted relative to either the vehicle frame or the engine, the tensioning device including a tensioning pulley disposed forwardly of the main drive pulley, and transversely from the fan drive assembly. The tensioning pulley engages the slack portion of the belt whereby the slack portion defines approximately a right angle.
In accordance with another aspect of the present invention, the tensioning device includes means biasing the tensioning pulley into engagement with the slack portion of the belt with a relatively constant biasing force during movement of the engine relative to the vehicle frame.